JAIST study reveals marine bacterium that targets cancer and protects healthy organs

A research team led by Professor Eijiro Miyako and Doctoral Student Mikako Miyahara from the Materials Chemistry Frontiers Research Area at the Japan Advanced Institute of Science and Technology (JAIST) has discovered that the marine bacterium Photobacterium angustum exhibits remarkable therapeutic effects against colorectal cancer. Their findings were published in the Journal for ImmunoTherapy of Cancer.

Groundbreaking cancer immunotherapies such as immune checkpoint inhibitors and CAR-T cell therapy have already been developed. However, they face challenges including high costs, immune-related adverse events, limited efficacy in solid tumors, and immunosuppressive mechanisms in the tumor microenvironment.

The research group has been developing bacterial cancer therapy which combines photosynthetic bacteria with resident bacteria within tumors.

In this study, the researchers evaluated the antitumor activity of multiple marine bacterial strains in mouse models of colorectal cancer. The results demonstrated only P. angustum showed remarkable antitumor effects and significantly prolonged survival. Other bacterial strains caused mouse death within two days of administration due to high toxicity.

Amongst the mice administered P. angustum, no weight loss or hematological abnormalities were observed. No signs of toxicity were detected in complete blood count, biochemical analysis, or histological examination. Additionally, the elevation of inflammatory cytokines was markedly lower compared with toxic strains, and bacteria were not detected in any vital organs except the liver after 24 hours.

Intravenously administered P. angustum selectively accumulated in tumor tissue, and numerous colony formations were confirmed. Meanwhile, almost no colonization was observed in healthy organs such as the heart, lungs, kidneys, and spleen.

The antitumor effect of P. angustum is thought to involve multiple mechanisms. These include direct destruction of cancer cells by natural exotoxins (such as hemolysins) produced by the bacteria, as well as the promotion of T cell, B cell, and neutrophil infiltration into tumors and the enhanced production of inflammatory cytokines such as TNF-α and IFN-γ.

P. angustum demonstrated remarkable antitumor effects not only in inflammation-induced colorectal cancer models but also in drug-resistant triple-negative breast cancer models. This suggests the possibility of application to cancer types other than colorectal cancer.

This study demonstrated that natural bacteria requiring no genetic modification can function as a safe and effective cancer immunotherapy. Going forward, the team plans to verify efficacy in various cancer types, evaluate combinatory effects with immune checkpoint inhibitors, and conduct detailed analysis of long-term immunological memory. Furthermore, elucidating the tumor-selective colonization mechanisms and molecular mechanisms of immune activation of P. angustum is expected to lead to the development of more effective treatments.

Journal Information
Publication: Journal for ImmunoTherapy of Cancer
Title: Systemic administration of Photobacterium angustum promotes antitumor immunity and direct tumor lysis in murine models of colorectal cancer
DOI: 10.1136/jitc-2025-012665